1. Field of the Invention
Aspects of the present invention relate to an apparatus for and a method of controlling battery discharge, and more particularly, to an apparatus for and a method of controlling a battery discharge status, which minimizes a number of battery switching operations by detecting a remaining voltage capacity of each of a plurality of batteries for supplying a battery-powered electronic device with power.
2. Description of the Related Art
Portable electronic devices are generally battery-powered and may use multiple batteries to extend an operating time thereof. Typically, a dual battery system having an internal battery and an external battery is widely used.
In operating the dual battery system having an embedded internal battery and a detachable external battery, the external battery is first used and the internal battery is then used depending on the discharge status of the external battery to extend the operating time of the system.
FIG. 1 is a block diagram of a conventional apparatus having dual batteries and controlling battery discharge. The conventional apparatus includes an internal discharge controller 11, an internal discharge switch 12, an internal battery 13, an external discharge controller 15, an external discharge switch 16, an external battery 17, and a main controller 14.
The internal discharge controller 11 and the external discharge controller 15 control operations of the internal discharge switch 12 and the external discharge switch 16, respectively. The main controller 14 detects a remaining voltage capacity of each of the internal battery 13 and the external battery 17 to allow the internal discharge controller 11 and the external discharge controller 15 to control discharges of the internal battery 13 and the external battery 17, respectively. In addition, the main controller 14 allows a charger (not shown) to charge the internal battery 13 and the external battery 17.
The internal discharge switch 12 and the external discharge switch 16 are switched on or off according to commands issued from the internal discharge controller 11 and the external discharge controller 15, respectively, to determine which one of the internal battery 13 and the external battery 17 is to be used.
The main controller 14 controls the external discharge controller 15 to use the external battery 17 first. Accordingly, the external discharge controller 15 instructs circuitry of the external discharge switch 16 to allow the external battery 17 to be used.
Once the external battery 17 is used, the main controller 14 starts to detect the remaining capacity of the external battery 17. If the remaining capacity is smaller than a predetermined threshold, the main controller 14 controls the external discharge controller 15 to interrupt the use of the external battery 17. Accordingly, the external discharge controller 15 controls the circuit connected to the external discharge switch 16 so that the external battery 17 is not used.
In addition, the main controller 14 controls the internal discharge controller 11 to use the internal battery 13. Accordingly, the internal discharge controller 11 instructs circuitry of the internal discharge switch 12 to allow the internal battery 13 to be used.
While the internal battery 13 is in use, the main controller 14 detects a remaining capacity of the internal battery 13. If the remaining capacity of the internal battery 13 is smaller than a predetermined threshold, the main controller 14 controls the circuit connected to the internal discharge switch 12 so that the internal battery 13 is not used. The main controller 14 controls the internal discharge controller 11 to stop using the internal battery 13.
These operations are performed until the internal battery 13 and the external battery 17 are completely discharged. After the internal battery 13 and the external battery 17 are completely discharged, no more power is supplied to the apparatus.
With regard to a time at which the main controller 14 detects the remaining capacity of the internal battery 13 or the external battery 17 supplies the apparatus with power, the main controller 14 detects the remaining capacity of the internal battery 13 or the external battery 17 when the internal battery 13 or the external battery 17 is loaded.
In such instances, however, the remaining capacity levels of the internal battery 13 detected by the main controller 14 are ones that no-load voltages are not taken into consideration, which may cause undesirably repeated switching operations between the internal battery 13 and the external battery 17. As a result, unstable voltages may be applied to the apparatus.
FIG. 2 is a graphical representation of voltage curves 20 produced by a conventional apparatus having dual batteries. Referring to FIG. 2, reference numerals 22 and 24 represent voltage-versus-time plots indicating voltage levels for the internal battery 13 and the external battery 17, respectively, as detected by the main controller 14.
As described above, in the apparatus having the internal battery 13 and the external battery 17, the external battery 17 is first used and the internal battery 13 is then used depending on the discharge status of the external battery 17. Thus, the voltage levels for the internal battery 13 are maintained and the voltage levels for the external battery 17 decline over time.
When the voltage level of the external battery 17 becomes smaller than a predetermined threshold 26, the apparatus is configured such that power supply from the external battery 17 is interrupted and power supply from the internal battery 13 is initiated, that is, switching from the external battery 17 to the internal battery 13 occurs.
The voltage levels of the external battery 17 and the internal battery 13, which are detected by the main controller 14, may vary, depending on whether the load is applied to the external battery 17 or the internal battery 13. In other words, if the external battery 17 or the internal battery 13 is loaded, the voltage levels of the loaded one of the external battery 17 and the internal battery 13 will slightly decrease and the main controller 14 detects a corresponding voltage drop.
Accordingly, at an instant when power supply from the external battery 17 is interrupted and power supply from the internal battery 13 is initiated, connection of an electrical load with the external battery 17 is cut off and the remaining voltage capacity of the external battery 17 is slightly increased, as detected by the main controller 14. If the detected remaining voltage capacity is greater than the predetermined threshold 26, the main controller 14 controls power supply from the internal battery 13 to be interrupted and power supply from the external battery 17 to be initiated, by which switching from the external battery 17 to the internal battery 13 occurs.
However, the voltage level of the external battery 17 detected in a state in which the external battery 17 is unloaded is not reliable for use in performing switching. If an electrical load is connected to the external battery 17 as the result of switching from the external battery 17 to the internal battery 13 and again to the external battery 17, the voltage level of the external battery 17 is reduced again, meaning that switching from the external battery 17 to the internal battery 13 occurs again.
In other words, the main controller 14 which has detected a state in which the external battery 17 is unloaded and has considered the no-load voltages of the external battery 17 as being the remaining voltage capacity derived from the actual voltage levels, causes frequent switching operations between the internal battery 13 and the external battery 17, so that unstable voltages may be applied to the apparatus.
In Korean Published Application No. 1999-48426 a conventional controller generates an interruption signal produced by comparing an output voltage of a battery with a predetermined voltage and converting an operation mode from a shut-down mode to a normal mode only when a second interruption control signal is generated.
According to the conventional apparatus, a voltage level is monitored in a state in which the no-load voltage of the battery is taken into consideration, a second interruption generation signal is generated responsive to the monitored voltage level to switch from the shut-down mode to the normal mode. The conventional controller controls battery power switching in an apparatus using a single battery and makes no provision for controlling battery power switching between an internal battery and an external battery in a dual battery apparatus.